1. Field of the Invention
The present invention relates to a circuit board and a method for manufacturing the same, and more specifically, to a circuit board on which an electronic component is mounted, and a method for manufacturing the same.
2. Description of the Related Art
A circuit board including laminated ceramic layers is known. FIG. 11 is a diagram illustrating a configuration in which an existing circuit board 500 is mounted on a printed wiring board 600. An electronic component 700 is mounted on the circuit board 500.
As shown in FIG. 11, the circuit board 500 includes a main body 501 and external electrodes 502 and 503. The main body 501 includes laminated ceramic layers, and is a hard board. The external electrodes 502 and 503 are provided on an upper surface and a lower surface, respectively, of the main body 501.
Further, the printed wiring board 600 is, for example, a mother board mounted in an electronic device, such as a cellular phone, and includes a main body 601 and external electrodes 602 as shown in FIG. 11. The main body 601 is a hard board formed from a resin or the like. The external electrodes 602 are provided on an upper surface of the main body 601.
Further, the electronic component 700 is, for example, a semiconductor integrated circuit, and includes a main body 701 and external electrodes 702. The main body 701 is a semiconductor substrate. The external electrodes 702 are provided on a lower surface of the main body 701.
As shown in FIG. 11, the circuit board 500 is mounted on the printed wiring board 600. Specifically, the circuit board 500 is mounted by the external electrodes 502 being connected to the external electrodes 602 via solder.
As shown in FIG. 11, the electronic component 700 is mounted on the circuit board 500. Specifically, the electronic component 700 is mounted by the external electrodes 503 being connected to the external electrodes 702 via solder. The circuit board 500, the printed wiring board 600, and the electronic component 700 described above are mounted in an electronic device, such as a cellular phone.
The existing circuit board 500 has a problem in that there is the possibility that the circuit board 500 will detach or separate from the printed wiring board 600. Specifically, due to an impact generated when the electronic device in which the circuit board 500 and the printed wiring board 600 are mounted is dropped, the printed wiring board 600 may be bent. Even when the printed wiring board 600 is bent, the circuit board 500 does not greatly deform so as to follow the bending of the printed wiring board 600, because the circuit board 500 is a hard board. Thus, a load is applied to the solder that connects the external electrodes 502 to the external electrodes 602. As a result, the solder may break and the circuit board 500 may detach or separate from the printed wiring board 600.
In order to overcome such a problem, sheets that are made of a flexible material are laminated to produce the circuit board 500. As such a circuit board produced by laminating sheets made of a flexible material, for example, the printed circuit board described in Japanese Unexamined Patent Application Publication No. 2006-93438 is known. It should be noted that for the configuration of the printed circuit board 800, the structure shown in FIG. 11 is used.
As shown in FIG. 11, the printed circuit board 800 described in Japanese Unexamined Patent Application Publication No. 2006-93438 includes a main body 801 and external electrodes (lands) 802 and 803. The main body 801 includes laminated sheets that are made of a thermoplastic resin. The external electrodes 802 and 803 are provided on an upper surface and a lower surface, respectively, of the main body 801. Similarly to the circuit board 500, the printed circuit board 800 is mounted on the printed wiring board 600 via the external electrodes 802 on the lower surface. In addition, similarly to the circuit board 500, the electronic component 700 is mounted on the printed circuit board 800 via the external electrodes 803 on the upper surface.
However, in the printed circuit board 800 described in Japanese Unexamined Patent Application Publication No. 2006-93438, there is the possibility that the electronic component 700 will be detached or separated therefrom. Specifically, since the printed circuit board 800 includes the sheets made of the flexible material, the printed circuit board 800 can be bent. Thus, even when the printed wiring board 600 is bent, the printed circuit board 800 can be bent in accordance with the bending of the printed wiring board 600. Therefore, breakage of the solder that connects the external electrodes 602 to the external electrodes 802 and detachment or separation of the printed circuit board 800 from the printed wiring board 600 are suppressed.
Meanwhile, the printed circuit board 800 has flexibility across the entire surface thereof. Thus, the printed circuit board 800 is bent across the entire surface thereof. On the other hand, the electronic component 700 includes a semiconductor substrate, which cannot significantly bend. Thus, a load is applied to the external electrodes 702 and 803 and the solder that connects the external electrodes 702 and 803. As a result, the solder breaks or the external electrodes 702 and 803 are separated from the main bodies 701 and 801. In other words, the connection between the electronic component 700 and the printed circuit board 800 is broken.